1. Field of the Invention
The present invention relates to a vehicle power supply system that supplies power from in-vehicle generator and battery to an external electrical device.
2. Background Art
There is a system in which an in-vehicle generator is used not only to supply power to electrical components, such as headlights and control devices, but also to supply power to a home electrical appliance, such as a refrigerator and a microwave oven while driving of a vehicle is stopped.
The vehicle power supply system in the related art detects a fluctuation of an electrical load of the home electrical appliance on the basis of an output of the generator, and controls a target rotational speed of an engine so that the detected output of the generator neither exceeds nor falls short of the electrical load. Hence, power comparable to the output of the generator is supplied to the home electrical appliance via a power convertor. More specifically, in a case where an electrical load of the home electrical appliance increases and an output voltage value of the generator falls below a pre-set threshold value, an engine speed is increased. On the other hand, in a case where power is excessively supplied to the home electrical appliance and an output current value falls below a threshold value, the engine speed is decreased. An example of this configuration is described, for example, in Patent Document 1.    Patent Document 1: JP-A-2010-68622
The vehicle power supply system in the related art is, however, a system that detects whether an output of the generator exceeds or falls short of the electrical load of the home electrical appliance first, and then controls the engine speed according to the detection value. Hence, power corresponding to the electrical load is not supplied at a time point when an output of the generator is detected and the power corresponding to the electrical load is supplied with a delay after the control. This configuration therefore makes it impossible to supply power quickly in response to an increase of power that the home electrical appliance requires from the generator (hereinafter, referred to as the required power). In other words, even when the home electrical appliance increases the required power from the generator, the generator fails to instantaneously supply power comparable to the required power. Hence, the home electrical appliance cannot perform an operation to be accomplished with the required power until the control according to a new detection value is performed. Further, in the case of a home electrical appliance that needs large power at start-up, for example, a home electrical appliance that drives a motor, the home electrical appliance may not be started by an output of the generator at start-up. Also, in the case of a small-size engine, such as the one in a motorcycle, an abrupt increase of the required power causes a load torque of the engine to increase and such an increase of the load torque decreases speeds of the generator and the engine. Hence, there is a risk that the engine stops before the engine speed is controlled (a phenomenon so-called engine stall).